Despite all of our efforts to keep our collections clean, tidy, and pest-free, there simply will come a time when we’re forced to pull out the “big guns” in our arsenal of commercial pesticides. Your stewardship of their use is an important aspect of orchid culture.

When selecting a pesticide, the very first thing you must do is properly identify the pest you are interested in eradicating. For example, insecticides are ineffective on mites, and disinfectants and fungicides do nothing for either! Likewise, a topical spray will have little-to-no effect on hard scale, thanks to their protective shells, and usually requires a systemic insecticide. Then, having identified the pest, you should also consider the environment in which you'll be treating your plants, including the potential presence of children and pets, or whether foul odors (often added to tell you the pesticide is present) will be a problem.

Once you have chosen the specific product to use, you should consider the following general pesticide use guidelines:

READ THE LABEL, and read it completely, including not only the application instructions, but be especially careful to read – and heed – the safety warnings and recommended protective gear.

Preventive treatment with pesticides is a mistake. As there is no way to totally kill all critters with a single treatment, that’s how resistant strains are developed. Use pesticides as a curative measure only. Insect Growth Regulators (IGR’s, such as Enstar II) are less of an issue in this regard, as they kill all maturity stages of insects and prevent them from reproducing, which precludes the possibility of passing on the resistant genes.

Rotate your pesticides. Different classes of chemicals have different modes of action on the pests. At one end of the spectrum are those that suffocate the insect (oils) or simply remove protective coatings (soaps) and make them vulnerable to the environment around them, while at the other end are those that disrupt biological processes in one or more of several different ways. Varying the mode of action between bouts of infestation is the best way to ensure maximum effectiveness and prevent the development of resistance. It is not necessary to use several pesticides for a single outbreak, but if you get another outbreak in the future, it is better to switch to a new one then.

Follow the label directions explicitly in terms of the concentration to use, the frequency of application, and the period between those applications.One of the most common issues that folks have with pesticide use is that of improper treatment: Too weak of a concentration seems obvious, in that it simply won’t kill the pests, but too strong of a mix concentration can also be bad, as not only might it be damaging to the plants, in some cases it will negatively affect the solubility of the active ingredient, rendering it less effective.

Most pesticides do not kill insects in all stages of their maturity – egg, larva, pupa, adult – so while a single treatment might kill, for example, all of the adults present, there are more critters waiting to mature and take their places devouring our plants. Insecticide labels recommend repeating the treatment – usually two or three times – so be sure to do just that. The time period between treatments is dependent on both the pesticide and the life cycle of the pest.If the chemical has extended residual action, the time period between treatments may be longer. If it doesn’t, such as is the case with home remedies concocted from soaps and alcohols, more frequent treatments will be necessary. Likewise, pests with short life cycles will need more frequent treatments to avoid missing the maturation and reproduction of an entire generation.

Failure to comply with any of these guidelines can fail to control the pests and may lead to the development of resistant strains that are even harder to eradicate.